Temperature stratification and insect pest populations in stored wheat with suction versus pressure aeration

Authors: Arthur, Franklin; Casada, Mark

Submitted to: Applied Engineering in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2016
Publication Date: 5/15/2016
Citation: Arthur, F.H., Casada, M.E. 2016. Temperature stratification and insect pest populations in stored wheat with suction versus pressure aeration. Applied Engineering in Agriculture. 32(6):849-860. doi:10.13031/aea.32.11757.

Interpretive Summary: Recent studies have shown benefits of using suction aeration, pulling cool air down through the grain mass, as opposed to standard pressure aeration, pushing air up through the grain mass. We further examined this technique by conducting a three-year study to assess temperatures at selected points in the bin headspace and below the surface of stored hard red winter wheat, and also assessed aeration cycles conducted in late summer, early autumn, and late autumn. During the early and late autumn cooling cycles, suction aeration cooled wheat faster than pressure aeration. Primary insect pest populations were also lower in the bins with suction aeration compared to pressure aeration, but there was little difference in populations of two fungus-feeding insect species. Results indicate suction aeration could be used instead of pressure aeration as part of insect pest management strategies to reduce insect pest populations without the use of chemical pesticides, but refinements and alterations of technique, such as a more precise positioning of the activation thermostat, may be necessary.

Technical Abstract: A three-year study was conducted to compare temperature profiles in the headspace and in the bulk mass of wheat aerated through pressure aeration and suction aeration. Insect pitfall traps were used to measure naturally-occurring populations of stored product insects. Results show uniform distribution of temperatures in the headspace until the area immediately above the top of the grain mass. In general, suction aeration cooled the top portion of the grain mass more quickly than pressure aeration, as measured by actual temperatures, days above specified temperature thresholds, and total heat accumulations above those thresholds, for each of the three years. Populations of Cryptolestes ferrugineus (Stephens), the rusty grain beetle, and Tribolium castaneum Herbst, the red flour beetle, were generally at least 2x to 4x greater in pressure versus suction aeration, depending on the specific sampling date, during the first two years of the study. An extensive infestation that developed during the third year may have diminished the effects of aeration. The other two insect species caught in abundance were two fungus-feeding insects, Typhaea stercoria (L.), the hairy fungus beetle, and Ahasverus advena (Waltl), the foreign grain beetle. Mixed effects were observed for these two species under the two aeration treatments. Results show that suction aeration may be preferable over pressure aeration, but afternoon temperatures lead to a buildup of heat in the headspace that affected the temperature of the upper layer of the grain mass. Installing a thermostat for controlled aeration utilizing the headspace temperatures as a set point instead of relying on outside ambient temperatures may increase efficiency of suction aeration.